Use the right log marker functions

According to [1] _LI() should be used for LOG.info(), _LE() for
LOG.exception() and LOG.error(), _LW() for LOG.warning().
The log marker functions must only be used when the message is
sent directly to the log.
Debug level log messages should not be translated.

[1] http://docs.openstack.org/developer/oslo.i18n/guidelines.html

Change-Id: Ib9f92ef6696b9a95ddae74f0d4a0a557c06ecc91
Merge "Use the right log marker functions"